Method of producing alkyl compounds of lead



Patented Jan. 13, 1942 I METHOD OF PRODUCING ALKYL COM- POUNDS OF LEAD George Calingaert and Harold A. Beatty, Detroit, v Mich., assignors to Ethyl Gasoline Corporation,

Detroit, Micla, a corporation of Michigan No Drawing.

Application February 16, 1938,

Serial No. 190,876

14 Claims.

Our invention relates to homoand heterotetraalkyl compounds of lead and to mixtures thereof. The object of the present invention is to provide new modes for producing these compounds and mixtures thereof. These are useful as antiknocks in motor fuels.

In carrying out our invention we take a tetraalkyl lead compound or a mixture of such compounds, which compound or mixture contains at least two different alkyl radicals, and cause it to react to redistribute the alkyl radicals between the lead atoms present, and produce a mixture of tetraalkyl lead compounds containing all or substantially all of the possible combinations of the alkyl radicals used. Referring, as an example, to the methyl and ethyl tetraalkyl lead compounds, the five possible compounds are the two homoalkyl compounds: tetramethyl lead and tetraethyl lead, and the three hetero-alkyl compounds: trimethylethyl lead, dimethyldiethyl lead and methyltriethyl lead.

We can take a mixture of any two or more of these compounds, or we can take any one of the hetero-alkyl compounds, and cause it to react to produce a mixture of all five compounds. Such a mixture constitutes a good antiknock.

As a specific example of one mode of carrying out our invention to produce such a mixture, we place in a vessel, by weight, 267 parts of tetramethyl lead, 323 parts of tetraethyl lead, and 200 parts of a-solvent such as hexane, and add 3 parts of anhydrous aluminum chloride. This mixture is stirred and the temperature is raised to-about 85 C. and maintained there for about two hours. The resulting product, which has been obtained in yields better than 95 per cent, contains, by weight, approximately 5.5 per cent tetramethyl lead, 24 per cent trimethylethyl lead, 37.5 per cent dimethyldiethyl lead, 26 per cent methyltriethyllead, and 7 per cent tetraethyl lead.

As another specific example of a mode of carrying out our invention to produce such a mixture, we place in a vessel a mixture, by weight, of 590 parts of dimethyldiethyl lead and 200 parts of a solvent, such as hexane, and add 3 parts of anhydrous aluminum chloride. This is stirred and the temperature is raised to about 85 C. and maintained there for about two hours. The resulting product is substantially the same in yield and composition as that obtained in the first specific example. i

In each of' the above two examples, we have In all such cases the composition of the final ma-- terial will be the same.

The method of carrying out our process described in the above specific examples may be varied in many ways.

The ratio of methyl to ethyl radicals in the material used may be changed as desired, from that given in the above specific examples, and

the resulting product will be a mixture of the same five lead compounds, but in different proportions. For example, if the compound methyltriethyl lead alone is used, or if the same proportions of methyl to ethyl radicals is secured by using 267 parts of tetramethyl lead and 970 parts of tetraethyl lead, the resulting mixture will contain, by weight, approximately 0.3 per cent of tetramethyl lead, 4.3 per cent trimethylethyl lead, 20.1 per cent dimethyldiethyl lead, 42.2 per cent methyltriethyl lead and 33.1 per cent tetraethyl lead. It appears that, for any ratio of methyl to ethyl radicals, the relative proportions of the live lead compounds present in the product correspond substantially to what would be expected if the methyl and ethyl radicals were redistributed on the four valences of the lead atoms in accordance with the law of random distribution.

The amount of aluminum chloride used may be more or less than the amount specified in the above examples, and we have obtained a good reaction with one-fifth of that amount, but when the amount is reduced substantially, the rate of reaction decreases. The reaction takes place at room temperature or below, but we may use elevated temperatures in order to bring the process to completion in a shorter time, and'temperatures of 130 C. or more may be used.

Other catalysts may also be used such as diethyl zinc, zinc fluoride, mercuric chloride, boron trifiuoride, dimethylaluminum chloride, zirconium chloride, phosphorus trichloride, and ferric chloride. The exact nature of the compounds which enter the reaction and which we term the active form of the catalyst is not known, and by the term catalyst we mean substances as above described which are put into thereaction mass. V r. r

The use of solvents is not essential, and good results have been obtained without their use, but they assist in maintaining the desired conditions a of operation. Other solvents, including decahydronaphthalene and kerosene may be used in the place of hexane. The proportion of the solvent may bevaried within wide limits, and good results have been obtained with ten times the amount given in the above specific examples.

I In order to avoid excessive or even violent reactions, it is advisable to add the catalyst last and cautiously, especially when little or no solvent is used.

The time and temperature, and the amount of solvent and catalyst may be varied according to the desired conditions of operation and the nature of the reagents employed.

Our process is not limited to tetraalkyl lead compounds containing only methyl and ethyl radicals, and may be applied to compounds in which other alkyl radicals are present. In each case the suitable conditions or operation will be determined by the reactivities of the starting materials. For example, diethyldi-n-propyl lead, or dimethyldiisobutyl lead, or a mixture of tetramethyl lead and tetra-n-propyl lead, are sufii ciently reactive to give satisfactory results under the conditions described in the above specific examples, while the reaction of a less reactive compound such as trimethyl-t-butyl lead is very small under these conditions. In the-latter case increasing the temperature increases the rate of reaction.

Our process may be varied in other ways. The reactions as described above may be stopped before completion, and the product will contain the various lead compounds in proportions different from those reached if the reaction were carried to completion. The mixture produced in our process may be separated into two or more fractions, and any undesired fractions may be used in a subsequent reaction. We may remove part or all of one or more given compounds continuously or intermittently while the reaction is in progress, and when this is done more of these particular compounds is formed at the expense of the others. Referring to the methyl and ethyl compounds of lead, by carrying out this process to the end, tetramethyl lead and tetraethyl lead may be obtained exclusively from any mixture, while any one of the three hetero-alkyl compounds may be obtained as the sole product if the methylethyl ratio in the starting mixture is adjusted to equal that of the desired compound. As a further variation of this continuous process, we may adjust the methyl-ethyl ratio and the separation process so that we obtain two or more of the five compounds in anydesired proportions.

We claim:

1. A method of making a mixture of lead tetraalkyl compounds containing lead mixed-alkyl compounds, which comprises producing by means of a catalyst an interchange of alkyl radicals between lead tetraalkyl molecules, there being at least two different alkyl radicals present.

2. A method of making a mixture of lead tetraalkyl compounds containing lead mixed-alkyl compounds, which comprises producing in solution by means of a catalyst an interchange of alkyl radicals between lead tetraalkyl molecules, there being at least two diiierent alkyl radicals present.

3. A method of making a mixture of lead tetraalkyl compounds containing lead mixed-alkyl compounds, which comprises producing by heating and by means of a catalyst an interchange of alkyl radicals between lead tetraalkyl molecules, there being at least two different alky] radicals present.

4. A method of making a mixture of lead tetraalkyl compounds containing lead 'mixed-alkyl compounds, which comprises producing in solution by heating and by means of a catalyst an interchange of alkyl radicals between lead tetraalkyl molecules, there being at least two different aikyl radicals present.

5. The method of making a mixture of methyl and ethyl tetraalkyl lead compounds containing the methyl-ethyl mixed-alkyl lead compounds, which comprises producing by means of a catalyst an interchange of methyl and ethyl radicals between lead tetraalkyl molecules.

6. The method of making a mixture of methyl and ethyl tetraalkyl lead compounds containing the methyl-ethyl mixed-alkyl lead compounds, which comprises producing in solution by means of a catalyst an interchange of methyl and ethyl radicals between lead tetraalkyl molecules.

'7. The method of making a mixture of methyl and ethyl tetraalkyl lead compounds containing the methyl-ethyl mixed-alkyl lead compounds, which comprises producing by heating and by means of a catalyst an interchange of methyl and ethyl radicals between lead tetraalkyl molecules.

8. The method of making a mixture of methyl and ethyl tetraalkyl lead compounds containing the methyl-ethyl mixed-alkyl lead compounds, which comprises producing in solution by heating and by means of a catalyst an interchange of methyl and ethyl radicals between lead tetraalkyl molecules.

9. A method of making a mixture of lead tetraalkyl compounds containing lead mixed-alkyl compounds, which comprises producing by means of a catalyst an interchange of alkyl radicals between lead tetraalkyl molecules, there being at least two different alkyl radicals present and separating from the reaction mass a part of the lead alkyl compounds formed while the reaction is in progress.

10. The method of making a mixture of methyl and ethyl tetraalkyl lead compounds containing the methyl-ethyl mixed-alkyl lead compounds. which comprises producing by means of a catalyst an interchange of methyl and ethyl radicals between lead tetraalkyl molecules and separating from the reaction mass a part of the lead compounds formed while the reaction is in progress.

11. The method of making a mixture of methyl and ethyl tetraalkyl lead compounds containing the methyl-ethyl mixed-alkyl lead compounds, which comprises producing in solution by heating and by means of a catalyst an interchange of methyl and ethyl radicals between lead tetraalkyl molecules and separating from the reaction mass a part of the lead compounds formed while the reaction is in progress.

12. A method of making a mixture of lead tetraalkyl compounds containing lead mixedalkyl compounds, which comprises producing by means of a catalyst an interchange of alkyl radicals between lead tetraalkyl molecules, there being at least two different alkyl radicals present and stopping the reaction before it has gone to completion.

13. A method of making a mixture of lead tetraalkyl compounds containing lead mixedalkyl compounds, which comprises producing by means of a catalyst taken from the group consisting of anhydrous aluminum chloride, mercuric chloride, ferric chloride, and zirconium chloride,

an interchange of alkyl radicals between lead tetraalkyl molecules, there being at least two different alkyl radicals present.

14. The method of making a mixture of methyl and ethyl tetraalkyl lead compounds containing the methyl-ethyl mixed-alkyl lead compounds, which comprises producing by means of a catalyst taken from the group consisting of anhydrous aluminum chloride, mercuric chloride, ferric chloride, and zirconium chloride, an interchange of methyl and ethyl radicals between lead tetraalkyl molecules.

GEORGE CALINGAERT. HAROLD A. BEATTY.

CERTIFICATE OF CORRECTION. Patent No. 2,270,108. January 15, 19l 2.

GEORGE CALINGAERT, ET AL.

It is hereby certified that error appears in the above numbered patent requiring correction as follows: In the grant, line 5, and in the heading to the printed specification, line 6, state of incorporation of assignee for "Michigan" read -Delaware-, as shown by' the record of assignment in this office; and that the said Letters Patent should be read' with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 2nd day of June, A. D. 1912.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents. 

